Dozens of people have been injured after two subway cars collided in the South Korean capital Seoul, BBC reported.
Emergency services said 78 people had been hurt. Some media reports put the number injured as high as 170.
One train ran into the back of another that had stopped between stations because of mechanical problems on one line, Yonhap news agency reports.
The accident comes as the nation continues to mourn the deaths of about 300 people in a ferry disaster.
The Sewol ferry sank with 476 people aboard - most of them high school students and teachers - off South Korea on 16 April.
President Park Geun-hye apologised earlier in the week amid mounting public anger and criticism over the way the rescue was handled.